A rally in Alphabet Inc. shares is poised to shake up the ranking of the world’s most valuable companies, amid signs the search giant is making headway in efforts to rival Nvidia Corp.’s bestselling AI accelerator.

European stocks posted their worst week since August as a risk-off mood hit some of this year’s biggest winners on concerns about lofty technology valuations and an uncertain US monetary policy outlook.

It’s not the time to bet against the biggest US technology names, according to short-seller Carson Block, even as warnings rise about a potential bubble in artificial intelligence.